PHYSICAL AND FAUNAL EVOLUTION 59 



from 115 to 215 feet of strata beneath the Black River, and resting 

 disconformably upon the Lower Beekmantown (Theresa formation), 

 which, with its basal sandstone (called Potsdam by Gushing), has a 

 maximum thickness of 140 feet. Gushing restricts the term Lowville 

 to the upper 75 to 85 feet of pre-Black River strata, separating the 

 lower part, on paleontologic grounds, as the Pamelia limestone. 

 At Lowville and elsewhere this series overlaps the Beekmantown, 

 resting with a basal sandstone upon the crystallines. The Pamelia 

 fauna is an Upper Stones Ri\'er fauna, according to Ulrich, while 

 the fauna of the Lowville is compared with that of the Upper Ghazy.' 



In the Ganadian region, only Upper Ghazy (Lowville and pos- 

 sibly the Pamelia equivalent) is present. In a number of localities 

 it rests directly upon the pre-Gambrics, generally with a basal sand- 

 stone (St. Mary's sandstone). In some cases, however, lower beds 

 (Beekmantown, with basal sands) have been reported. In Min- 

 nesota and Wisconsin the Upper Ghazy is called Stones River, though 

 it represents only the upper part of the Stones River formation of 

 Safford's Tennessee section where the thickness is 360 feet. The 

 Minnesota beds are 32 feet thick and are probably the exact equiva- 

 lent of the Lowville of New York, though the fauna is stated to be 

 more like that of the Pamelia. The relation of these beds to the 

 underlying St. Peter sandstone is significant, since the contact is per 

 fectly conformable and gradational. Moreover, Stones River fossils 

 {Hormotoma gracilis, Lophospira perangulata, etc.) are found in 

 some of the upper beds of the St. Peter, showing that with the 

 advent of the Ghazy sea, the sand dunes of the St. Peter desert were 

 incorporated as basal sands in the overlying formation. This meant, 

 of course, a slight reworking of the sands by the encroaching sea. 

 That this reworking did not reach to the bottom of the St. Peter, at 

 least not in all cases, is shown by the persistence of the folds and faults 

 in the lower beds, whereas they are absent in the upper (see Fig. 4). 

 A comparison of sections shows that in general lower beds of Ghazy 

 age appear progressively above the St. Peter as we proceed southward 

 and eastward. The relationship of these beds to the St. Peter 

 has not been discussed in detail, but it is certain that in some localities, 

 at least, the gradation observed in Minnesota obtains. The relation- 



I See dishing, loc. cit. 



